software raytrace: correctly handle backface lighting

WickedEngine/shaders/ddgi_raytraceCS.hlsl

@@ -115,6 +115,11 @@ void main(uint3 DTid : SV_DispatchThreadID, uint3 Gid : SV_GroupID, uint groupIn
 			ray.Origin = ray.Origin + ray.Direction * hit.distance;
 			hit_depth = hit.distance;
 
+			if (hit.is_backface)
+			{
+				surface.flags |= SURFACE_FLAG_BACKFACE;
+			}
+
 			if (!surface.load(hit.primitiveID, hit.bary))
 				break;
 

WickedEngine/shaders/raytraceCS.hlsl

@@ -128,6 +128,11 @@ void main(uint3 DTid : SV_DispatchThreadID, uint groupIndex : SV_GroupIndex)
 		// ray origin updated for next bounce:
 		ray.Origin = ray.Origin + ray.Direction * hit.distance;
 
+		if (hit.is_backface)
+		{
+			surface.flags |= SURFACE_FLAG_BACKFACE;
+		}
+
 		if (!surface.load(hit.primitiveID, hit.bary))
 			return;
 

WickedEngine/shaders/raytracingHF.hlsli

@@ -50,6 +50,7 @@ struct RayHit
 	float2 bary;
 	float distance;
 	PrimitiveID primitiveID;
+	bool is_backface;
 };
 
 inline RayHit CreateRayHit()
@@ -57,6 +58,7 @@ inline RayHit CreateRayHit()
 	RayHit hit;
 	hit.bary = 0;
 	hit.distance = FLT_MAX;
+	hit.is_backface = false;
 	return hit;
 }
 
@@ -102,6 +104,7 @@ inline void IntersectTriangle(
 		hit.distance = t;
 		hit.primitiveID = prim.primitiveID();
 		hit.bary = float2(u, v);
+		hit.is_backface = det > 0;
 
 		if (prim.flags & BVH_PRIMITIVE_FLAG_TRANSPARENT)
 		{
@@ -159,6 +162,7 @@ inline bool IntersectTriangleANY(
 			hit.distance = t;
 			hit.primitiveID = prim.primitiveID();
 			hit.bary = float2(u, v);
+			hit.is_backface = det > 0;
 
 			Surface surface;
 			surface.init();

WickedEngine/shaders/surfel_raytraceCS.hlsl

@@ -107,6 +107,11 @@ void main(uint3 DTid : SV_DispatchThreadID)
 			ray.Origin = ray.Origin + ray.Direction * hit.distance;
 			hit_depth = hit.distance;
 
+			if (hit.is_backface)
+			{
+				surface.flags |= SURFACE_FLAG_BACKFACE;
+			}
+
 			if (!surface.load(hit.primitiveID, hit.bary))
 				return;
 

WickedEngine/wiVersion.cpp

@@ -9,7 +9,7 @@ namespace wi::version
 	// minor features, major updates, breaking compatibility changes
 	const int minor = 60;
 	// minor bug fixes, alterations, refactors, updates
-	const int revision = 21;
+	const int revision = 22;
 
 	const std::string version_string = std::to_string(major) + "." + std::to_string(minor) + "." + std::to_string(revision);